The spread of tuberculosis may have killed off leprosy in Europe in the Middle Ages, according to research published in the latest issue of the Royal Society Proceedings B.

A collaborative study led by University College London (UCL) scientists, following the discovery of a shrouded body in a sealed chamber overlooked by tomb robbers, found evidence of both diseases in a range of archaeological remains dating from the 1st to the 15th centuries.

An initial examination of the body, currently under analysis in Israel , revealed signs of co-infection of TB and leprosy in the bone tissue. The collaborative team, led by Dr Helen Donoghue and Dr Mark Spigelman from UCL's Centre for Infectious Diseases and International Health, went on to identify co-infection in ancient bones around Europe , where the DNA of the bacteria behind both diseases was detected in 42 per cent of the samples examined.

In the Middle Ages leprosy was a widespread, much-feared disease which unaccountably declined around the same time that tuberculosis began to spread across Europe. TB went on to become a major long-term epidemic disease, with one-third of the world's population now infected and more than 8 million new cases in the year 2000 alone.

Researchers now believe that the two trends were no coincidence. In fact, the new findings suggest that TB overtook leprosy as the more aggressive, faster-killing disease.

Dr Mark Spigelman says: "We stumbled across this discovery while examining a shrouded body excavated by Israeli archaeologist Dr Shimon Gibson. The body from around Jerusalem dated from the 1st century AD, when the normal burial practice was to wrap it in a shroud, then return after a suitable time and rebury the bones in an ossuary.

"In this case, the shrouded body had not been re-buried. We thought there must have been a reason for this, so we decided to look for signs of leprosy - a cause of fear and stigma at the time - in addition to the tuberculosis which we had already found to be present."

Dr Helen Donoghue says: "After finding both diseases in the body, we re-examined other samples from sites around ancient and mediaeval Europe and realized that we were looking at a fairly common, previously unrecognised phenomenon of co-infection.

"Scientists have previously speculated over whether cross-immunity might have protected tuberculosis patients from leprosy. However, our findings suggest a different explanation.

"A weakening of the immune system following infection by leprosy, coupled with the stress, poverty and malnutrition associated with the social isolation and stigma of living with the disease, could have paved the way for opportunistic co-infection by TB which brought a speedier death. In time this would reduce the number of individuals suffering from leprosy, leading to its overall decline."

Notes to the Editor:

For more information or to set up an interview, please contact Jenny Gimpel at the UCL Media Relations Office on +44 (0)20 7679 9739, Out of Hours: +44 (0)7917 271364 or e-mail j.gimpel@ucl.ac.uk.

The following institutions took part in this study: Centre for Infectious Diseases and International Health, University College London, UK; Department of Anthropology, University of Szeged, Hungary; Paleo-DNA Laboratory, Lakehead University, Ontario, Canada; Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University, Jerusalem, Israel; Archaeological Research Laboratory, Stockholm University, Sweden